LINE CLEANING SYSTEM AND MEASUREMENT

Abstract: A method for the removal of debris and other unwanted matter from the bore of a blind tubular line (38) including measuring the length of the bore once it has been cleared. The cleaning and measurement method includes inserting an elongate tube (12) into the bore of the line (38), injecting (12, 14) a compressed gas through the elongate tube (38) and extracting by suction (32) from the end of the line at which the tube enters debris and other unwanted matter from the gap between the tube and the inner wall of the line, attaching a flexible elongate member to a camera insertible in the said bore in such a manner that an end portion of the said member is detected by the said camera when the camera is moved along the said bore, moving the camera and the said member attached thereto along the said bore until the said member is detected by the camera to reach the blind end of the tubular bore, and measuring the length of the said elongate member which has been fed into the tubular line to reach the said blind end.

Description: Line Cleaning System and Measurement This invention relates to a line cleaning and measurement system, and more particularly to a system for the cleaning and measurement of instrument lines, ie tubular lines having an internal bore through which an instrument may be inserted. During the construction and commissioning of chemical plants it is necessary to inspect the bores of a large number of instrument lines prior to the insertion of instrument probes. The inspection often reveals that such lines contain debris such as water, cleaning solvents, swarf, grinding and other construction debris. The instrument lines are usually 'blind', being completely closed at one end, and often terminate in a reduced diameter instrument pocket into which the instrument probe locates. Most of these instrument pockets are located inside closed vessels, some of which are up to 25m below the top of the line. The instrument lines will often be curved in order to position the instrument probe at the desired location. Since the lines are of a small diameter, typically 20mm, removal of the debris is both expensive and time consuming when conventional means are used. Cutting of the instrument lines allows them to be partially cleaned by conventional means. However, this does not solve the problem of debris in the bottom part of the line, ie that part which is inside the closed vessel. A problem caused by the presence of debris in instrument lines is the mislocation of instrument probes during their insertion. A conventional method of locating probes is to feed a probe down an instrument line until it can go no further. In situations where debris is present in the line the probe may stop short of the instrument pocket and thereby, upon plant start up, provide information to the plant operators from the wrong location, with potentially disastrous consequences. A method for cleaning the inner surface of a heat exchanger tube is described in British Patent Specification No. 1,103,488 in which a pressurised fluid, supplied from a tube located within the heat exchanger tube, is deflected against the inner surface of the heat exchanger tube in a direction concurrent with the flow of fluid through the heat exchanger tube so as to carry away material removed from the inner surface. Such a system, however, is incapable of clearing curved lines. European Patent Application No. 0 029 980 discloses an apparatus for clearing debris from a drilled cavity by blowing pressurised gas into the cavity and removing the ejected debris by suction. However, this apparatus would be ineffective for clearing tubular lines. According to a first aspect of the present invention there is provided a method for the removal of debris and other unwanted matter from the bore of a blind tubular line to be cleaned, the method including inserting an elongate tube into the bore of the line, injecting a compressed gas through the elongate tube and extracting by suction from the end of the line at which the tube enters the line debris and other unwanted matter from the gap between the tube and the inner wall of the line. It should be appreciated that the phrase "blind tubular line" includes tubular lines which terminate with a blank end or a pocket as well as tubular lines which are temporarily blanked off, for example by the insertion of a body, such as a bung or a probe, into the line. Where the blind end comprises a pocket a further member, eg a measurement transducer may be carried in the pocket. Advantageously, the tube is inserted into the line through an applicator having an attachment which is attached to a corresponding attachment on an end of the line, the applicator also having an outlet through which said debris and other unwanted matter is extracted. Preferably, a source of compressed gas is connected to the free end of the tube, the source being switchable whereby gas may be injected when required by an operator. Desirably, a suction pump is connected to the outlet of the applicator, the suction pump being switchable whereby debris and other matter may be extracted when required by an operator. The tubular line to be cleaned may be an instrument line and, in particular, a thermocouple line. Such an instrument line may terminate in an instrument pocket having a reduced average diameter. Conveniently, the tube may terminate in a reduced average diameter portion having an external diameter less than the internal diameter of the instrument pocket, the reduced diameter portion of the tube being insertable into the instrument pocket. Desirably, the tube is slidably located within the line by means of a resilient packing member contained within the applicator. Preferably, the method includes manipulating the tube within the line so as to dislodge the debris and other matter into the gap between the tube and the line in order that the debris and other matter may be removed by suction. Conveniently, the compressed gas pressure may be less than or equal to 150 psi (1.03 x 10 6 Nm~ 2 ) . Preferably, the method of the invention may include the steps of attaching the applicator to the tubular line, inserting the elongate tube into the bore of the line, passing compressed gas down the tube so as to dislodge the debris and other unwanted matter inside the bore of the line, activating the suction pump connected to the outlet of the applicator, manipulating the tube within the bore of the line so as to direct the debris and other matter into the gap between the tube and the bore of the line so that the debris and other matter becomes carried by the suction- assisted gas flow, and removing the debris and other matter through the outlet of the applicator by suction. According to a second aspect of the present invention there is provided a method of measuring the length of the bore of a blind tubular line which includes the steps of removing debris from the line in accordance with the method of the first aspect described above, attaching a flexible elongate member to a camera insertible in the said bore in such a manner that an end portion of the said member can be detected by the said camera when the camera is moved along the said bore, moving the camera and the said member attached thereto along the said bore until the said member is detected by the camera to reach the blind end of the tubular bore, and measuring the length of the said elongate member which has been fed into the tubular line to reach the said blind end. The said elongate member may comprise wire, cable, tape, fibre or the like. The camera may be a closed circuit tv camera which may be attached via one or more suitable cables to an image processing unit and video display unit outside the said line so that a remote operator can observe the image detected inside the bore. The said elongate member may be attached to the camera by means of the said cable or cables. The said end portion of the elongate member may protrude beyond the camera viewing head to facilitate detection by the camera. The said camera may have an associated actuator device, eg including one or more stepper motors, which may be controlled remotely which provides movement of the camera along the bore. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a part sectional view of a line cleaning system, and Figure 2 is, to an enlarged scale, part of the line cleaning system of Figure 1. Referring now to the Figures, a line cleaning system 10 is shown comprising a 12mm diameter flexible tube 12 having one of its ends connected to a supply of compressed air (not shown) and its other end connected to a short length of 3mm diameter tube 14 via a diameter reducing means 16. The tube 12 is slidably located through a resilient packing member 18, the packing member 18 having been fitted into one end 20 of a pipe 22 having a branch 24. The other end 26 of the pipe 22 is connected to a flanged pipe 28 whilst the end 30 of the branch 24 is connected to a vacuum line 32, in turn connected to a vacuum pump (not shown). The flange 34 of the flanged pipe 28 is aligned with and connected to a flange 36 of an thermocouple line 38, the thermocouple line 38 having an internal bore of 20mm. The thermocouple line 38 terminates in an thermocouple pocket 40 having a reduced diameter portion 42 of diameter 7mm into which a thermocouple probe (not shown) is locatable. The tube 12 passes through the packing member 18 and the pipe 22 into the thermocouple line 38 so that the tube 14 is locatable in the reduced diameter portion 42 of the thermocouple pocket 40. The tube 12 and the thermocouple line 38 together define an annulus 44 and the tube 14 and the portion 42 together define a further annulus 46. Prior to operation of the system 10, a miniature closed circuit television (CCTV) inspection camera (not shown) is inserted into the thermocouple line 39 to establish whether any debris is present. If fine debris such as grinding dust, swarf, filings or fluid are present then the system may be used for their removal. The flanged pipe 28, with the branched pipe 22 attached to it, is connected to the flange 36 of the thermocouple line 38 and the vacuum line 32 is connected to the branch 24. The tube 12 is then fed through the packing member 18 and the pipe 22. The supply of compressed air is switched on and the air pressure is gradually increased towards a maximum of 150 psi (1.03 x 10 6 Nm~ 2 ) . The tube 12 is then fed into the thermocouple line 38 thereby blowing all the loose debris to the bottom (as shown in the Figures) . Whilst the air is still blowing, the vacuum pump is switched on. The tube 12 is manipulated up and down within the line 38 in order to dislodge debris from the reduced diameter portion 42 of the thermocouple pocket 40. This has the effect of blowing the debris into the annulus 44 between the tube 12 and the line 38 so that the debris becomes airborne in the vacuum-assisted airflow and is thereby removed via the vacuum line 32. As debris is progressively removed, the tube 14 become engaged with the reduced diameter portion 42 and the airflow blows any remaining debris from the portion 42 into the annulus 46 and from there into the annulus 44 from whence it is removed by the vacuum-assisted airflow. After a suitable period of time the compressed air supply is switched off and the tube 12 is withdrawn. The vacuum pump is switched off and the line 38 is then re-inspected using the miniature CCTV inspection camera (not shown) . If debris remains in the line 38, the tube 12 is re-inserted and the cleaning procedure repeated as necessary. Once it has been established that the line 38 is free from debris (by using the minature CCTV inspection camera as described above) , it is desirable to measure the length of the line 38. A nylon wire of a suitable length is attached to the umbilical of the CCTV camera (which provides power to the camera and passes detected signals to a remote monitor) in such a manner that the leading end of the wire protrudes beyond the camera head by approximately 100mm. The camera is again fed down the line 38 such that the leading end of the wire can be viewed by the camera to enter the reduced diameter portion 42 of the thermocouple pocket 40. The length of nylon wire which has been fed into the line 38 is then measured thereby providing a measurement of the length of the line 38. Trials have shown the length measurement to be accurate to about + 50mm for a 25m long line. This enables the thermocouple to be made to the correct length so that the thermocouple probe locates fully into the termocouple pocket 40.

Claims: Claims 1. A method for the removal of debris and other unwanted matter from the bore of a blind tubular line to be cleaned, the method including inserting an elongate tube into the bore of the line, injecting a compressed gas through the elongate tube and extracting by suction from the end of the line at which the tube enters the line debris and other unwanted matter from the gap between the tube and the inner wall of the line. 2. A method as in Claim 1 and wherein the tube is inserted into the line through an applicator having an attachment which is attached to a corresponding attachment on an end of the line, the applicator also having an outlet through which said debris and other unwanted matter is extracted. 3. A method as in Claim 1 or Claim 2 and wherein a source of compressed gas is connected to the free end of the tube, the source being switchable whereby gas may be injected when required by an operator. 4. A method as in Claim 2 and wherein a suction pump is connected to the outlet of the applicator, the suction pump being switchable whereby debris and other matter may be extracted when required by an operator. 5. A method as in any one of the preceding Claims and wherein the said line is an instrument line. 6. A method as in Claim 5 and wherein the line is a thermocouple line. 7. A method as in Claim 5 or Claim 6 and wherein the thermocouple line terminates in an thermocouple pocket having a reduced average diameter. 8. A method as in Claim 7 and wherein the tube terminates in a reduced average diameter portion having an external diameter less than the internal diameter of the thermocouple pocket, the reduced diameter portion of the tube being insertable into the thermocouple pocket. 9. A method as in Claim 2 and wherein the tube is slidably located within the line by means of a resilient packing member contained within the applicator. 10. A method as in any one of the preceding Claims the method including manipulating the tube within the line so as to dislodge the debris and other matter into the gap between the tube and the line in order that the debris and other matter may be removed by suction. 11. A method as in any one of the preceding Claims and wherein the compressed gas pressure is less than or equal to 150 psi (1.03 x 10 6 Nm~ 2 ). 12. A method as in any one of the preceding Claims, the method including the steps of attaching the applicator to the tubular line, inserting the elongate tube into the bore of the line, passing compressed gas down the tube so as to dislodge the debris and other unwanted matter inside the bore of the line, activating the suction pump connected to the outlet of the applicator, manipulating the tube within the bore of the line so as to direct the debris and other matter into the gap between the tube and the bore of the line so that the debris and other matter becomes carried by the suction-assisted gas flow, and removing the debris and other matter through the outlet of the applicator by suction. 13. A method of measuring the length of the bore of a blind tubular line which includes the steps of removing debris from the line in accordance with the method of any one of the preceding Claims, attaching a flexible elongate member to a camera insertible in the said bore in such a manner that an end portion of the said member can be detected by the said camera when the camera is moved along the said bore, moving the camera and the said member attached thereto along the said bore until the said member is detected by the camera to reach the blind end of the tubular bore, and measuring the length of the said elongate member which has been fed into the tubular line to reach the said blind end. 14. A method as in Claim 13 and wherein the camera is a closed circuit tv camera which is attached via one or more suitable cables to an image processing unit and video display unit outside the said line so that a remote operator can observe the image detected inside the bore. 15. A method as in Claim 13 or Claim 14 and wherein the said camera has an associated actuator device, eg including one or more stepper motors, which is controlled remotely and which provides movement of the camera along the bore. 16. A method as in Claim 13 and wherein the said elongate member comprises wire, cable, tape, fibre or the like. 17. A method as in any one of Claims 13 to 16 and wherein the said elongate member is attached to the camera by means of the said cable or cables. 18. A method as in any one of Claims 13 to 17 and wherein the said end portion of the elongate member protrudes beyond the camera viewing head to facilitate detection by the camera. 19. A method for the removal of debris and other unwanted matter from the bore of a tubular line substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawing.

Inventors: BARRETT CARSTEN LAWRENCE, STATHAM ROY, WILKINS JOHN, BARRETT, CARSTEN, LAWRENCE, STATHAM, ROY, WILKINS, JOHN
Applicants: BARRETT CARSTEN LAWRENCE, BRITISH NUCLEAR FUELS PLC, STATHAM ROY, WILKINS JOHN, BARRETT, CARSTEN, LAWRENCE, STATHAM, ROY, WILKINS, JOHN
Application year: 1994
Main classification: B08B5
IPC codes: B08B5, B08B9, G01B11